Roundneck Sexton Beetle

 Highlighted Species:

Roundneck Sexton Beetle

Nicrophorus orbicollis

(Coleoptera: Silphidae)

Image: Roundneck sexton beetle (Nicrophorus orbicollis) with phoretic mites (Fry, 2020).

About:

The roundneck sexton beetle is a burying beetle in the Northeastern U.S. which has an important role breaking down carrion into nutrients. As the name burying beetle suggests, these beetles bury dead animals as a way to feed and raise their young. In the process, decomposing animal bodies are quickly processed back into the nutrient cycle both as food for the young beetles and for the many other organisms that will feed.

Image: Sexton beetles are common across Eastern North America, particularly where moist soil can be found (Naterpillar, 2024).

Nicrophorus orbicollis males will seek out carrion with highly sensitive antennae attuned to the odors of decay. The male will release pheromones to attract a female to the carrion as a way of courting her. Males will fight over this valuable commodity. If the female beetle accepts the gift, the two will dig a hole near the animal body and drag it down to bury it. Working quickly, burying beetles pass on fungus and bacteria to the decaying animal which aid in breaking down tissues. When secured, the female creates a brood chamber within and lays her egg. The buried dead animal will provide both food and shelter as it develops. 

Image: Nat's partner is incredibly supportive of her hobbies, even when he thinks taking pictures with roadkill is unpleasant (Naterpillar, 2024).

Sexton beetles exhibit some amount of parental care, as they will feed the growing larva on regurgitated carrion. Additionally, burying beetles have a mutualistic relationship with phoretic mites. These tiny red mites will ride on the backs of adult beetles, transporting them between sources of carrion. Once introduced to the buried animal, the mites defend against competitor insects like maggots and nematodes, leaving more food for the larval beetle.

Image: Please note, this decaying squirrel may not be representative of the actual stage of decay that sexton beetles prefer; it was simply the only carrion available then to pose with (Naterpillar, 2024).

As with many carrion-seeking insects, there is a specific window of time post-death which attracts them. Because of their reliable, innate sense to detect a corpse, burying beetles such as the roundneck sexton beetles are of forensic importance to humankind when a deceased person is found outside. Forensic succession is the order that various insects and other organisms will appear at a corpse By understanding insect biology, the time of death of a human body can be predicted by counting the species, life stage, and populations of insects present at a corpse. 

Design Notes:

    A black base with four bold patches of orange represent the roundneck sexton beetle. Although no phoretic mites can be seen, they will surely be picked up by my beetles at some point.

Image: the bold orange against black is a type of warning coloration (Naterpillar, 2024).

Resources:

Cannon, R. (2020, March 17). Phoresy: Mites hitchhiking on
burying beetles. Ray Cannon’s nature notes.
https://rcannon992.com/2020/03/15/
phoresy-mites-hitchhiking-on-burying-beetles/ 

Fry, R. (2020, July 25). Roundneck Sexton beetle (Nicrophorus      orbicollis). iNaturalist.     https://www.inaturalist.org/observations/54294351

Joseph, I., Mathew, D., Sathyan, P., & Vargheese, G.
(2011). The use of insects in forensic investigations:
An overview on the scope of forensic entomology.
Journal of Forensic Dental Sciences, 3(2), 89.
https://doi.org/10.4103/0975-1475.92154 

Roundneck Sexton beetle (Nicrophorus orbicollis).
JungleDragon. (n.d.). https://www.jungledragon.com
/specie/20290/roundneck_sexton_beetle.html 

White, P. S., Morran, L., & de Roode, J. (2017). Phoresy.
Current Biology, 27(12).
https://doi.org/10.1016/j.cub.2017.03.073